Given a newly generated PullReview - Should notify the Adopt OpenJDK group

The work flow should now be changed to allow the Adopt OpenJDK group to peer-review patches before they are submitted to Mentors. (ensures quality of patches / ideas)

The state transition is: OPEN -> PENDING_PEER_REVIEW.

To do this, there are two main changes we need to make:

1. Implement the actual state transition in the PullReviewModifier
2. Email the Adopt OpenJDK group.

Note that task 2 will need to depend upon #65 (implementing the email actor).

Finally ensure documentation is updated please :)

Working with Martin on this.